The overall goal of the proposed research is to understand the control of the elongation phase of transcription by RNA polymerase II. This control process is mediated by negative factors which cause RNA polymerase II to synthesize only short transcripts after initiation from a promoter and positive factors that allow release from this early block in elongation. A Drosophila in vitro system will be used to further characterize three factors that were recently identified as being involved in controlling this transition from abortive elongation into productive elongation. The C- terminal domain (CTD) of the large subunit of RNA polymerase II has been implicated in the control process and its role will be further examined. The function of P-TEFb as a CTD kinase operating during elongation will be defined. The involvement of factor 2 as a potential ATP dependent termination factor and as a factor required for the elongation control process will be examined. The role of P-TEFa and search for other factors that may be involved will be continued. Although the ultimate goal is to generate a defined system that mimics initiation and elongation control in vivo, the feasibility of using a simple defined elongation control system consisting of pure RNA polymerase II, a dC-tailed template, and a set of elongation control factors will be examined. It is vital to understand the elongation control process because it is involved in controlling a large number of genes including many oncogenes and viral transcription units including HIV-1. It is likely that the study of this controlling step in eucaryotic gene expression will lead to a better understanding of the aberrant behavior of cancer cells and the process that controls the transcription of the HIV-1 genome.